The use of hydrogen to evaluate in situ biochemical and chemical reactions has been restricted to some extent by the limited availability of simple, robust hydrogen detection methods.   Sampling technology has advanced to a point where dissolved hydrogen can be sampled in the field and shipped to a fixed base laboratory for analysis; however, only a few laboratories have the capability to make environmentally significant nanomolar measurements.  This presentation describes a simple device constructed with readily available materials that offers adequate sensitivity to measure environmentally useful levels of hydrogen in gas or liquid samples.  The device consists of the following primary components: (1) a flow system to sweep the sample through the device; (2) a sample injection port; (3) a sample conditioning unit to remove water and gases that may interfere with the detector;  (4) a metal oxide gas sensing semi-conductor-based detection unit and power supply; and (5) a data acquisition component.  A prototype device was constructed, tested, calibrated, and used to evaluate the hydrogen concentration in a wetlands remediation system consisting of a zero-valent iron treatment component and an anaerobic bioremediation component.  Applications, performance, and limitations of the device will be presented.